Experimental methods for analyzing the response of the coronary vascular bed have been based principally on obtaining and analyzing mean pressure and flow data from the ascending aorta and left anterior descending coronary artery. The input impedance of both the ascending aorta and the left anterior desending coronary artery and the transfer function for the pressure and flow-wave forms of the intervening segment have not been analyzed extensively. Analysis of this using a rigorous mathematical approach (Fourier Analysis) may well permit more sophisticated interpretation of the effects of various stresses on the physical properties of the arterial wall. The close approximation of canine impedances to human impedances has been documented. Fifteen canines will undergo thoracotomy with catheterization for pressure monitors in the ascending aorta, left anterior descending coronary artery and the right or circumflex coronary artery. Flow probes will be placed on each of these vessels. Thereafter, the animal will be subjected to a series of stresses in order to quantify the response of the heart and the coronary vessels to these stresses. The input impedances and the transfer functions will be calculated. These will be analyzed to determine their changes from the normal control period for the individual animal. It is anticipated that this series of experiments will permit the evaluation of the use of this analytic technique in characterizing the behavior of the coronary vascular bed under these conditions of stress. The experiment will then be repeated using animals who have had an ameroid constrictor placed on the left anterior descending coronary artery so as to develop a chronically collateralized coronary arterial bed in the distribution of the left anterior descending artery. The impedance changes and transfer functions obtained in this group of animals will be compared with those obtained in the normal group of animals. This should permit characterization of the physical nature of the coronary collateral bed in terms of direct resistance effects, capacitance effects, and inertance effects. If, indeed, this is the case, the experiments will have proven the validity of a relatively simple, yet highly sophisticated tool, for use in coronary artery research.